1. Field of the Invention
The present invention relates to a plasma display panel and a drive method for the same.
2. Description of the Related Art
Generally, a plasma display panel (hereinafter, abbreviated to PDP) has many advantages whereby a thin and large screen display can be easily realized, the angle of view is wide, and the response speed is high. Therefore, recently, PDPs have been used as flat displays in the forms of wall-hung televisions, public bulletin boards and the like. PDPs are divided by operation methods into a direct current discharge type (DC type) to be operated in a direct current discharge condition where electrodes are exposed to a discharge space (discharge gas), and an alternating current discharge type (AC type) to be operated in an alternating current discharge condition where electrodes are coated with dielectrics and prevented from being directly exposed in a discharge gas.
In the DC type, discharge occurs during a period in which a voltage is applied, and in the AC type, discharge is continued by inverting the polarity of a voltage. Furthermore, the AC type is divided into two types, a type having two electrodes in one cell and a type having three electrodes in one cell.
Herein, the structure of the conventional 3-electrode AC type plasma display panel and a drive method therefor are explained. FIG. 2 is a cell sectional view showing an example of the conventional plasma display panel.
The 3-electrode AC type plasma display panel comprises front substrate 20 and back substrate 21 which are opposed to each other, a plurality of X electrodes 22 and Y electrodes 23, and data electrodes 29 disposed between the substrates 20 and 21, display cells disposed in a matrix form at intersections between the X electrodes 22 and Y electrodes 23 and the data electrodes 29.
A glass plate or the like is used for the front substrate 20, and the X electrodes 22 and Y electrodes 23 are provided at predetermined intervals. Metal electrodes 32 are laminated on the X electrodes 22 and Y electrodes 23 to lower wiring resistances. On these electrodes, transparent dielectric layer 24 and protective layer 25 made from MgO or the like for protecting the transparent dielectric layer 24 from discharge are formed. Meanwhile, a glass plate is used for the back substrate 21, and data electrodes 29 are provided so as to be orthogonal to the X electrodes 22 and Y electrodes 23. Furthermore, on the data electrode 29, white dielectric layer 28 and fluorescent layer 27 are provided. Between the two glass substrates, partitions are formed in parallel to the paper surface at predetermined intervals. The partitions form discharge spaces and partition or define pixels. Within the discharge space 26, a mixed gas of He, Ne, Xe, and the like is sealed. Such a structure is mentioned in “Society for Information Display 98 Digest”, p. 279-281, May 1998.
FIG. 1 shows a plan view of the conventional 3-electrode AC type plasma display panel. At intersections between Xi of X electrodes 22 and Yi of Y electrodes 23 (i=1 through m) and Dj of data electrodes 29 (j=1 through n), display cells 31 are arranged in a matrix form.
Next, a method for driving the PDP is explained. The current mainstream provides an address display separation method (ADS method) in which scanning periods and sustaining periods are separated. Hereinafter, a drive method for this ADS method is explained. FIG. 3 shows an example of a drive waveform diagram of one subfield (hereinafter, abbreviated to SF) 1 of the 3-electrode AC type plasma display panel. One subfield 1 is composed of three periods, that is, preliminary discharge period 2, scanning period 3, and sustaining period 4.
First, the preliminary discharge period 2 is explained. A negative preliminary discharge pulse 6 is applied to the X electrode 22, and a positive preliminary discharge pulse 5 is applied to the Y electrode 23. Thereby, a difference in formation of wall charges at the final point of the previous SF due to the emission condition of the previous SF is reset and initialized, and at the same time, all pixels are forcibly discharged, and a priming effect for subsequent writing discharge at a low voltage is obtained. In FIG. 3, each of the positive and negative preliminary discharge pulses 5 and 6 is generated once, however, each pulse may be divided to perform two roles so that a sustaining eliminating pulse for resetting the previous SF condition is applied, and thereafter a priming pulse for generating a priming effect by discharging all pixels is applied. At this time, the number of sustaining eliminating pulses is not limited to one, and different pulses may be applied several times. The priming effect is not required for each SF, there is also a method in which a priming pulse is applied only once per several SFs. The priming pulse causes all pixels to emit light regardless of displays. Therefore, by reducing the number of priming pulses to be applied, luminance for a black display can be suppressed to be low. As in the conventional example of FIG. 3, when the preliminary discharge pulses 5 and 6 are used, in order to set the priming effect for forcibly discharging all pixels so as to be once per several SFs, the preliminary discharge pulses 5 and 6 may be lowered in the SFs other than in FIG. 3 so as to perform only resetting. At this time, in order to make resetting secure, different pulses may be applied several times in place of the preliminary discharge pulses.
Next, the period enters the scanning period 3. In the scanning period 3, scanning pulses 7 are applied to the X1 through Xm of the X electrodes 22 in order. In accordance with the scanning pulses 7, data pulses 9 are applied to D1 through Dn of the data electrodes 29 in accordance with the display patterns. In a pixel to which the data pulse 9 has been applied, a high voltage is applied between the X electrode 22 and data electrode 29, so that writing discharge occurs, a great positive wall charge is formed at the X electrode 22 side, and a negative wall charge is formed at the data electrode 29 side. On the other hand, in a pixel to which the data pulse 9 has not been applied, the applied voltage is low, so that discharge does not occur, and the status of the wall charge does not change. Thus, depending on the existence of the data pulse 9, two statuses of wall charges can be created. The diagonal lines of the data pulses 9 in the Figure indicate that the existence of the data pulse 9 changes in accordance with display data.
When application of the scanning pulses 7 to all lines is finished, the period enters the sustaining period 4. Sustaining pulses 10 are alternately applied to all X electrodes 22 and all Y electrodes 23. The voltage values of the sustaining pulses 10 are set so as not to cause discharge by themselves. Therefore, in a pixel without occurrence of writing discharge, wall charge is little, so that discharge does not occur even when a sustaining pulse is applied. On the other hand, in a pixel in which writing discharge has been occurred, a great positive wall charge exists at the X electrode 22 side, this positive wall charge is superposed on the first positive sustaining pulse (referred to as a first sustaining pulse) applied to the X electrode 22 and, a voltage higher than the discharge starting voltage is applied to the discharge space, whereby sustaining discharge occurs. Due to this discharge, negative wall charges are accumulated at the X electrode 22 side, and positive wall charges are accumulated at the Y electrode 23 side. The next sustaining pulse (referred to as a second sustaining pulse) is applied to the Y electrode 23 side, and in response to superposition of the wall charge, sustaining discharge also occurs herein, and wall charges with a polarity opposite to that of the first sustaining pulse are accumulated at the X electrode 22 side and Y electrode 23 side. Thereafter, discharge still continuously occurs based on the same principle. That is, a potential difference caused by a wall charge generated due to the x-th sustaining discharge is superposed on the x+1-th sustaining pulse and the sustaining discharge is continued. A light emission amount is determined by the number of sustaining discharge continuance.
The whole of the abovementioned sustaining eliminating period 2, scanning period 3, and sustaining period 4 is referred to as a subfield. When gradation display is carried out, one field which is a period for displaying image information for one screen is comprised of a plurality of subfields. Gradation display can be achieved by changing the number of sustaining pulses of each subfield and turning each subfield on/off.
Thus, a display screen with m lines is driven in a progressive (non-interlace) manner by using m of X electrode drivers and one Y electrode driver.
However, in the abovementioned structure and drive method, non-discharge gap 38 which is the interval between the X electrode and the Y electrode in the next cell must be larger than the discharge gap 37, and this is not suitable for highly fine panels. Therefore, as generally known examples of a panel structure and a drive method suitable for high fineness, there are a plasma display panel drive method and a plasma display panel device described in Japanese Unexamined Patent Publication No. 160525 of 1997.
FIG. 4 shows a plan view of the panel. The points of difference from the conventional panel of FIG. 1 are that one Y electrode is added to the upper part, and all X and Y electrodes are disposed at equal intervals. In this conventional example of FIG. 4, the electrode gaps between all X and Y electrodes are pixels, and this can cope with highly fine screens.
FIG. 5 and FIG. 6 show the drive method. FIG. 5 shows a drive waveform of an odd-numbered field of the conventional example of FIG. 4. FIG. 6 shows a drive waveform of an even-numbered field of the conventional example of FIG. 4. The preliminary discharge period 2 is the same as in the conventional example of FIG. 3. Next, the scanning period 3 is entered. In the scanning period 3, scanning pulses 7 are applied to X1 through Xm of X electrodes 22 in order.
Data pulses 9 are applied in response to the scanning pulses 7 to D1 through Dn of the data electrodes 29 in accordance with display patterns. The method for applying the data pulses 9 at this time is shown in FIG. 7. In FIG. 7, Y1 to X3 on a certain data electrode of FIG. 4 are arranged horizontally. In the example of FIG. 7, a case of display by turning on and off is shown as in the upper part of the Figure. This drive method is interlace drive, so that the first, third, and fifth pixels in order from the left are caused to display in an odd-numbered field, and the second and fourth pixels are caused to display in an even-numbered field.
First, the case of an odd-numbered field is explained. Among the first, third, and fifth pixels, only the first pixel is a lighting pixel. Therefore, only when a scanning pulse 13 is applied to X1 which is the X electrode 22 of the first pixel, a data pulse 9 is applied. When application of scanning pulses 8 to all lines is finished, the period enters the sustaining period 4. In the odd-numbered field, odd-numbered X electrodes and even-numbered Y electrodes have the same phase, and even-numbered X electrodes and odd-numbered Y electrodes have the same phase. Thereby, in a pixel in which wall charge has been formed in the scanning period, sustaining discharge occurs between the odd-numbered X electrodes and even-numbered Y electrodes and between the even-numbered X electrodes and odd-numbered Y electrodes. In the conventional example of FIG. 7, sustaining discharge does not occur during the first sustaining, however, sustaining discharge occurs from the second sustaining, and thereafter, sustaining discharge is continued. If a wall charge is not formed in the scanning period, sustaining discharge occurs in neither of the odd-numbered fields and even-numbered fields.
Next, the case of an even-numbered field is explained. The second and fourth pixels are lighting pixels, so that data pulses 9 are applied both when a scanning pulse 13 is applied to X1 which is the X electrode 22 of the second pixel and when a scanning pulse 13 is applied to X2 which is the X electrode 22 of the fourth pixel. When application of scanning pulses 13 to all lines is finished, the period enters sustaining period 4. In an even-numbered field, odd-numbered X electrodes and odd-numbered Y electrodes have the same phase, and even-numbered X electrodes and even-numbered Y electrodes have the same phase. Thereby, in a pixel in which a wall charge has been formed in the scanning period, sustaining discharge occurs between the odd-numbered X electrodes and odd-numbered Y electrodes and between the even-numbered X electrodes and even-numbered Y electrodes. Also herein, in the second pixel, sustaining discharge does not occur during the first sustaining, however, as the odd-numbered field, sustaining discharge starts from the second sustaining and is continued thereafter.
As mentioned above, if the two odd-numbered and even-numbered fields are joined together, display can be carried out between all X electrodes and Y electrodes, so that a highly fine display can be realized.
Thus, by using m of X electrode drivers and two of Y electrode drivers, a display screen with 2 m lines which is two times the lines of the conventional example can be displayed. However, in this case, interlace drive is employed.
However, the number of scanning lines increases for realizing a highly fine panel. Accordingly, the number of scanning drivers also increases, and production costs increase. On the other hand, as shown in the prior art, a method may be used in which interlace drive is employed and the number of scanning drivers can be reduced. However, image quality deteriorates due to interlace drive.